BACKGROUND AND OBJECTIVES: Postoperative delirium (POD) in Surgical Intensive Care patients is an important independent outcome determinant. The purpose of our study was to evaluate the incidence and determinants of POD. METHODS: Prospective cohort study conducted during a period of 10 months in a Post-Anesthesia Care Unit (PACU) with five intensive care beds. All consecutive adult patients submitted to major surgery were enrolled. Demographic data, perioperative variables, length of stay (LOS) and the mortality at PACU, hospital and at 6-months follow-up were recorded. Postoperative delirium was evaluated using the Intensive Care Delirium Screening Checklist (ICDSC). Descriptive analyses were conducted and the Mann-Whitney test, Chi-square test or Fisher's exact test were used for comparisons. Logistic regression analysis evaluated the determinants of POD with calculation of odds ratio (OR) and its confidence interval 95% (95% CI). RESULTS: There were 775 adult PACU admissions and 95 patients had exclusion criteria. Of the remaining 680 patients, 128 (18.8%) developed POD. Independent determinants of POD identified were age, ASA-PS, emergency surgery and total amount of fresh frozen plasma administered during surgery. Patients with delirium had higher mortality rates, were more severely ill and stayed longer at the PACU and in the hospital. POD was an independent risk factor for hospital mortality DISCUSSION: There was a high incidence of delirium had a high incidence in intensive care surgical patients. POD was associated with worse severity of disease scores, longer LOS in hospital, and in PACU and higher mortality rates. The independent risk factors for POD were age, ASA-PS, emergency surgery and the amount of plasma administered during surgery.